Symptom: Occasionally Linux Mint 20 with Xfce boots up with no desktop icons and no background. The operating system works, but you have to use means other than the usual desktop icons to invoke programs.
Solution: On this computer, we can correct the problem if we invoke a terminal (with ctrl-alt-T or ctrl-alt-F2), delete the contents of ~/.cache/sessions/, then reboot.
Leave a comment if you have an explanation why this problem occurs or why this solution works.